1. Field of the Invention
The present invention relates to compact fan units for automobiles, and more particularly to a low-noise compact automobile fan unit.
2. Description of the Prior Art
Automobiles having an air conditioner unit generally include a temperature sensor such as a thermistor for detecting the temperature of air in the vehicle compartment, and a compact fan unit for circulating air to provide a uniform temperature distribution within the vehicle compartment. The temperature sensor is disposed at a proper position in a path of circulation of air so as to avoid a local air temperature detection.
The reliability of the above-mentioned temperature detection can be improved by increasing the rate of flow of the compact fan unit. Since the fan unit is disposed within the vehicle compartment, it is desired to increase the flow rate of the fan unit without increasing the size of the fan unit. The flow rate of the fan unit increases as the rotational speed of the fan unit is increased. However, a problem is found that increasing the rotational speed of the conventional fan unit raises the fan noise from about 35dB(A) to about 50dB(A) which is almost the upper limit of a required noise level for the vehicle compartment. Consequently, the conventional fan unit does not satisfy an increasing recent demand for a silent vehicle compartment.